regarding analog modules

hello guys,

i need a little help regarding analog modules.my doubts are as follows:

1.how resolution and span are decided in selecting analog modules.

2.what is the reason that integer value in siemens can go upto -27648 to +27647 where as in Allen Bradely it is 32767 and in GEFanuc it is 27400.

3.does this range has anything to do with resolution and span.

[schnippschnapp].

please do reply to this message as i am confused about how selection of analog modules are made.so even if these questions are not related to analog pls give the answers.

please refer to analog value representation in stantard Step7 help.

Shortly: 27648 is Siemens-invented number noone knows exactly why:) 27648-32512 means overflow (though you can handle them just as normal signal). 32512-32767 means errors.

Resolution is how many bits are significant. If we take 32767 till -32768 it's 15 bit+sign. So if module description holds AI 8*12 bit that means it has 8 channels, up to 12 bit each. 3 lowest bits are filled with zeroes. So smallest difference you can catch with such mode is 8 (i mean code).